Copper base alloys and process for preparing same



Sept. 12, 1967 COPPER BASE ALLOYS AND PROCESS FOR PREPARING SAME E. J.CAULE ETAL 3,341,369

Filed March 5, 1965 aoao N 6000 5 h g. 400 g Q 2000 Q E, 30-? 6% 8 U S20- Cu-IOZ Ni-O. 12 Cr 70 a0 BRASS/ 7O -80 BRASS 1st OX/DAT/O/V EMPEPATURE 4 CE/V T/GPADE INVENTORS. ELMER J. CAULE M/CHAEL J P/PVOR PH/L/P RSPER/PV ATTORNEV United States Patent ABSTRACT OF THE DISCLOSURE Thepresent invention relates to new and improved copper base alloys havingsubstantially improved resistance to oxidation and tarnishing in moistand contaminated atmospheres and the process for preparing said alloyssaid alloy having an oxidation resistant zone of at least 50 Angstromsin depth consisting of a discrete dispersion of oxide in the metalmatrix.

Copper base alloys have found wide and varied uses in industry andcommerce in general; however, the many useful physical properties ofthese alloys are almost invariably negated to some degree by theirextremely low resistance to oxidation and to tarnishing, especially inmoist and contaminated atmospheres. This poor oxidation resistance haslimited the utility of copper base alloys and has resulted in long andcontinuing efforts to overcome this disadvantage.

It has long been the object of the copper industry to develop new copperbase alloys which overcome these disadvantages and are characterized bygood oxidation resistance. The copper industry has aimed to develop newcopper base alloys whose resistance to oxidation and tarnishing is atleast as good as austenitic stainless steels. The previous approach tothis problem has been the investigation of the oxidation and tarnishingcharacteristics of hinary copper alloys where the binary allOyingaddition is strongly reducing in nature and which, by itself, growshighly protective oxidation films, for example, aluminum. This approachhas been unsuccessful in attaining stainless properties which areself-healing in everyday environments.

There has been some limited success where the binary alloys wereprocessed in such a maner as to completely prevent the oxidation of thecopper matrix while still permitting oxidation of the alloying addition,see, for example, Journal of the Institute of Metals, 63, 21 (1938), byL. E. Price and G. T. Thomas. This result has been usually attained byselective oxidation whereby the binary alloys are subjected to hightemperature treatment in atmospheres, such as moist hydrogen, which willoxidize the reducing alloying ingredient but which maintains the copper,with its lower free energy of oxidation, in the reduced condition. Thistype of treatment often produces protective, invisible, oxide films ofthe alloying addition. These films protect the copper matrix as long asthey are not mechanically damaged. When the films are mechanicallydamaged, as they are in even mild forming operations, such asstraightening sheet, involving less than 1 percent plastic deformation,they do not repair themselves spontaneously with protective copper oxidefree films at normal temperatures or in the atmospheres.

Accordingly,

absence of special it is an object of the present invention to provide aprocess for the preparation of new and improved copper base alloys whichhave substantial resistance to oxidation. 1

It is a further object of the present invention to provide new andimproved copper base alloys which are capable of substantial resistanceto oxidation under a Wid variety of conditions.

It is a still further object of the present invention to provide alloysas aforesaid, the oxidation resistance of which is not impaired when thealloy is mechanically dam aged, i.e., it is an object of the presentinvention to provide ennobled, oxidation-resistant copper base alloys.

Further objects and advantages of the present invention will appearhereinafter.

In accordance with the present invention it has now been found that theforegoing objects and advantages of the present invention may be readilyaccomplished and new and improved copper base alloys capable ofsubstantial resistance to oxidation may be prepared. The novel alloys ofthe present invention may be prepared by (A) providing from 2.0 to 25.0percent by Weight of two elements, with the ratio of the first to thesecond of said elements being from 0.03:1 to 10:1, the first of saidelements being selected from the group consisting of: aluminum; gallium;indium; and beryllium, the second of said elements being selected fromthe group consisting of: silicon; germanium; tin; and beryllium,provided that when beryllium is the second element, aluminum is thefirst element; (B) alloying said elements with copper; and (C) heatingsaid alloy in an oxidizing environment for at least one minute at atemperature of from 400 C. to the solidus temperature of the alloy toform a first outside layer 25 to 5000 Angstroms in depth of copperoxides and oxides of said alloying additions and a second oxidationresistant layer immediately beneath said first layer containing adiscrete dispersion of a complex oxide including at least one of saidalloying additions, said second layer being of a thickness of at least50 Angstroms and preferably substantially greater.

Under optimum conditions the first layer may be bright and shiny andoxidation resistant; however, When it is necessary to remove the firstlayer in order to provide brightness or to perform some mechanicaloperations, the second highly ennobled oxidation resistant layer remainsaifording considerable protection to the alloy.

Accordingly, the novel, highly oxidation resistant alloys of the presentinvention comprise: (A) from 2.0 to 25 percent by weight of two alloyingadditions and the balance essentially copper, with the ratio of thefirst to the second of said alloying additions being from 0.03:1 to10:1, the first of said alloying additions being selected from the groupconsisting of: aluminum; gallium, indium; and beryllium, the second ofsaid alloying additions being selected from the group consisting of:silicon; germanium; tin; and beryllium, provided that when beryllium isthe second alloying addition aluminum is the first alloying addition;and (B) said alloy having an oxidation resistant Zone of at least 50Angstroms in depth containing a discrete dispersion of a complex oxideincluding at least one of said alloying additions.

In accordance with the present invention the improved properties of thealloys of the present invention are imparted primarily by the discretedispersion of complex oxide including at least one of said alloyingadditions in a subsurface layer. These complex oxides are present in ametal matrix generally free from separated copper oxides and uponremoval of the first outside layer provide a bright and shiny articlehaving extensive resistance to oxidation, resistance to most aggressivechemical reagents and extensive resistance to further oxidation andtarnishing over a wide range of temperatures at or below the formationtemperature of the oxidation resistant zone. In addition, in some casesthe first outside layer is bright and shiny.

In addition to the foregoing, it is also surprising that the secondlayer containing the dispersed oxide is not brittle and does not sufferfrom grain boundary weaknes s. It is a surprising feature of the presentinvention that the alloys containing this dispersed oxide layer areductile and can be bent and formed by deep drawing.

The present invention is related in theory to copending application Ser.No. 281,992 by Michael J. Pryor, filed May 21, 1963, now US. Patent3,259,491. In accordance with said copending application, an oxidationresistant copper base alloy is formed by bulk alloying with copper atleast two alloying ingredients in concentration ratios to form certaincomplex oxides on the surface of the alloy, i.e., the alloyingingredients are added in concentration ratios so that they diffuse tothe surface of the alloy in proportion to the concentration of theindividual alloying ingredient in the complex oxide. The complex oxidesformed in said copending application are similar to and in someinstances the same as the complex oxides formed in the alloy of thepresent invention as a discrete dispersion in the oxidation resistantzone.

The above copending application provides an alloy representing aconsiderable advance in the art and affording a high degree of oxidationresistance. The alloys of said copending application are particularlyadvantageous at elevated temperatures and provide extensive oxidationresistance at, for example, 800 C. However, the disadvantage of thealloys of said copending application is that less protection is affordedover a wide range of temperatures, for example, from C. to 550 C. Saidcopending application discloses modifications which achieve a greaterdegree of oxidation resistance over a wide temperature range, but theprotection afforded while considerable still leaves room forimprovement.

It is the particular advantage of the present invention that extensiveoxidation resistance is achieved over a wide range of temperatures. Thisoxidation resistance is ob tained by a simple and convenient process andwith a surprisingly inexpensive alloy. The alloys and process of thepresent invention are especially surprising in view of the long andfruitless quest for a process which achieves an alloy of this type.

In accordance with the present invention a total of from 2 to 25 percentby weight of two elements are alloyed with copper. The amount from 2 to25 percent is the total combined weight of both elements which areadded. The first element is selected from the group consisting ofaluminum, gallium, indium and beryllium and the second element isselected from the group consisting of silicon, germanium, tin andberyllium, provided that when beryllium is the second element aluminummust be the first element.

The total combined amount of the first and the second element is from 2to 25 percent by weight and the preferred combined amount is from 2 to 7percent by weight. The relative ratio of the first to the second of saidelements must be maintained with the following ratio, from 0.03:1 to10:1. That is, the ratio of the first to the second of said elementsmust be maintained within the foregoing ratio. Naturally, the ratiowhich is chosen for a particular system will vary widely within theforegoing broad ratio depending upon the particular system and therelative atomic weights of the elements which are added. For example,when the alloying additions are aluminum and silicon, which ispreferred, the following ratio of aluminum to silicon should beemployed, from 2.5:1 to 0.5: 1. Similarly, for elements which have loweror higher atomic weights than aluminum, the ratio should be adjusted,for example, the beryllium-silicon system utilizes the following ratioof beryllium to silicon, 2.0:1 to 0.15:1. The indium-silicon systemutilizes the following ratio of indium to silicon, 10:1 to 02:1. Thegallium-silicon system utilizes the following ratio of gallium tosilicon, 10:1 to 0.2:1. The aluminum-germanium system utilizes thefollowing ratio of aluminum to germanium, 5:1 to 0.2:1 and thealuminum-tin system utilizes the following ratio of aluminum to tin, 3:1to 0.03:1. Similarly, the following ratios apply to the followingsystems: aluminum to beryllium, 10:1 to 0.511; gallium to germanium, 5:1to 01:1; gallium to tin, 3:1 to 0.121; indium to germanium, 10:1 to0.211; and indium to tin, 5.011 to 0.1:].

It should be noted that the exact proportion of the first alloyingaddition to the second alloying addition will be affected by the atomicweights of the respective elements, the specific complex oxides desiredto be formed, and also the diffusion and chemical characteristics of theparticular alloying additions.

As indicated above, it is a requirement of the present invention thatfrom 2 to 25 percent by weight of the two alloying additions are addedto copper and alloyed therewith. Naturally, the present inventioncontemplates within its scope the use of other materials in combinationwith copper and the two metal alloying additions in order to achieveparticularly desired results or to provide a particular alloy. Forexample, still greater oxidation resistance may be obtained by addingthe following in addition to the two principal alloying ingredients:boron; manganese; zinc; and beryllium where beryllium is not one of thealloying ingredients. Also, particularly desired properties may beenhanced by the addition of other alloying ingredients while retainingoxidation resistance.

In accordance with the present invention, the particular method ofalloying copper with the chosen alloying additions is not particularlyimportant and conventional methods may be readily employed provided thatthe molten copper to which the alloying elements are added is initiallyoxygen free so that the alloying elements are not present in the alloyas oxides prior to solidification. As is conventional, the elements maybe added as master alloys or in elemental form.

It is a critical aspect of the present invention, however, that afterthe alloying additions have been added to copper, the alloy solidifiedand if desired brought into a suitable or desired product form, theresultant alloy is heated in oxidizing environment for at least oneminute, and preferably at least five minutes, at a temperature of from400 C. to the solidus temperature of the alloy.

In the preferred embodiment, the alloy is heated in an oxidizingatmosphere, such as air, to desired temperatures at a rate of at least 5C. per hour. Naturally, the particular temperature of treatment willvary depending upon the particular system and the particular resultsdesired. However, in the preferred embodiment a temperature range offrom 500 C. to 850 C. is employed, and optimally a still more preferredrange of from 600 to 800 C. is used. The time of holding the alloy atthese elevated temperatures should for practical purposes be less than 2days, although longer heater times may be utilized if desired. Theoptimum heating time is from one (1) hour to 10 hours.

It is critical that the alloy be heated in an oxidizing environment. Anyoxidizing environment may be readily employed, for example, preferablyair or oxygen and also molten oxidizing salt baths may be employed, suchas those containing sodium nitrate.

After the alloy has been held under the above conditions the alloy ispreferably cooled to room temperature.

Under optimum treatment conditions, the foregoing process results in asurface which is bright and shiny. However, the outside surface is notthe oxidation resistant zone but comprises a thin first zone, normallyvarying in thickness from 25 to 5000 Angstroms depending upon the timeand temperature of treatment and the particular alloy utilized. Thefirst zone may, however, provide some oxidation resistance and it isoften desirable to retain the first zone. This first outside zone couldbe and often is mottled or darkened in appearance. The physicalcomposition of this first or outside zone is a thin layer of copperoxides which may contain in addition, the oxides associated with one orboth alloying additions either singly or in combination. For example, inan aluminum-silicon system, the first or outermost layer may containalumina, silica and also complex oxides of aluminum and silicon.

A conventional pickling may be employed to remove any surface blemishes.The pickling step assists in providing a uniformly shiny and brightphysical appearance by removing dark, discoloring, unsightly oxideswhich precede the formation of the more protective oxides during theoxidation heating. Naturally, the pickling procedure should not removethe second zone. Alternately, conventional metal removal techniques,such as mechanical bufiing and polishing, etc., may be used.

Where the outside zone is bright and shiny in appearance, some oxidationprotection may be afforded thereby. However, the principal oxidationprotection afforded by the alloys of the present invention is providedby the zone immediately beneath the first zone. This oxidation resistantsecond zone provides the major advantages of the present invention.

It is preferred, although not necessarily essential, to remove theoutside or first zone by any desired means in order to bare the secondzone. That is, after the first zone is removed, the outermost zone isthe second zone or oxidation resistant zone. The first zone may beremoved by any desirable means, such as pickling or bufiing or somemechanical forming operation.

The depth of the second zone will vary widely depending upon theparticular treatment conditions, with in all cases the thickness beingat least 50 Angstroms. In general, in order to provide reasonableoxidation protection, the second zone should be a minimum of 50Angstroms in depth and preferably at least 200 Angstroms. The maximumdepth of the second or oxidation resistant zone is completely dependentupon the treatment conditions and the particular system utilized, thatis, longer holding times and higher temperatures will provide a thickeroxidation resistant zone. Normally, however, a second or oxidationresistant zone of around 2 mils is the preferred value, although forsome uses it may be preferable to get a thicker oxidation resistant zoneor even if desired obtain an oxidation resistant zone which comprisesall of the rest of the alloy.

The oxidation resistant zone is characterized by containing a discretedispersion of complex oxides including at least one of said alloyingadditions. The discrete dispersion is present in the metal matrix. Thecomplex oxides are similar to and in some cases the same as the complexoxides in said copending patent application Ser. No. 281,992.

In accordance with the present invention the second or oxidationresistant zone is bright and shiny in appearance and provides theextensive oxidation resistance referred to hereinabove, that is,oxidation resistance over a wide temperature range at or below theformation temperature range. In other words, oxidation and tarnishresistance is provided in a bright and shiny alloy havingcharacteristics desired in alloys of thistype over a wide temperaturerange up to the temperature of the heat treatment step. This second oroxidation resistant zone behaves chemically as if it were a more noblemetal than copper, i.e., it resists chemical attack by many strongchemical reagents which are normally used for pickling copper.

Beneath the oxidation resistant zone is normally the copper base alloyitself. This base would normally have only the original oxidationresistance in the absence of the oxidation resistant zone of the presentinvention, but would not have the enhanced resistance.

The second or oxidation resistant zone depends for its formation on theinward migration of oxygen. Therefore, some equilibrium solubility foroxygen in the base metal is required. Hence, the principle of thepresent invention may be extended to an alloy system which hassignificant solubility for oxygen, e.g., iron, silver, gold andzirconium, with of course copper being preferred. The present inventionachieves an ennobling of the base alloy, i.e., makes the alloy behave asif it were a more noble metal.

In addition, the principle of the present invention may be extended toheating in anions other than oxygen, while at a temperature of 800 ofcourse oxygen is preferred. Examples of such other anions are:fluorides; carbides; phosphides; sulfides; nitrides; and dispersions ofintermetallics. Naturally, the base metal must have significantsolubility for the parv ticular anion.

The present invention will be more readily apparent from a considerationof the following illustrative examples.

EXAMPLE I EXAMPLE n The alloy prepared in Example I, in 10 mil sheet,cold rolled form, was carefully cleaned and heated for two hours atvarious temperatures from 350 to 800 C. The weight gain in microgramsper square centimeter is shown in the graph which is the drawing of thepresent application. This weight gain represents the initial oxidationwhich results in the copper-aluminum-silicon alloy. After the heating atthe temperatures of 350-600" C. the alloy was mottled and darkened incolor, although at 800 C. it remained bright and shiny in color.

As a comparative example the same copper-aluminumsilicon alloy in thesame form was cleaned and subjected to the treatment conditions of thepresent invention as follows: the specimen was first heated at 800 C.for 2 hours in air; followed by cooling to room temperature; followed byvigorously attacking for about seconds with an etchant composition of 10percent concentrated sulfuric acid, 40 percent concentrated nitric acidand 50 percent glacial acetic acid in order to remove about 800micrograms per square centimeters, i.e., in order to remove the first oroutside zone and to bare the second or oxidation resistant zone. Theresultant specimen was bright and shiny in appearance.

The resultant specimen was then reoxidized for two hours in thetemperature range between 350 and 800 C. The weight gain in microgramsper square centimeter may be seen in the drawing of the presentapplication.

was reduced to about one-third of that characteristic of the oherwiseuntreated base alloy. In the 350 C, temperature range, much largerreductions of oxidation rate of a factor of around one-twentieth areobtained. After the 2 hour oxidation treatment of the alloy of thepresent remained bright and shiny at all temperatures in contrast to thedarkened and mottled appearance of the copper-aluminum-silicon alloywhen given the single initial heating at 350 to 600 C.

For comparison purposes, relative oxidation rates of conventional copperbase alloys are shown in FIGURE 1. The alloys shown are: 70-30 brass;and a copper base alloy containing 10 percent nickel and 0.1 percentchromium.

EXAMPLE III A copper-aluminumberyllium alloy was prepared in the samemanner as Example I to have a composition as follows: 1.74 percentaluminum; 0.34 percent beryllium; and the balance essentially copper.

The alloy thus prepared, in 10 mil sheet cold rolled form, was thencarefully cleaned and heated in air at a temperature of 350 C. for 2hours. The total weight gain after the 2 hour heating period Was 38micrograms per square centimeter and the sample was mottled in color.

A fresh sample of the same copper-aluminum-beryllium alloy in the sameform was carefully cleaned and heated C. for 2 hours open to the airatmosphere. The sample was then cooled to room temperature andvigorously attacked with an etchant composition as in Example II inorder to remove about 2300 micrograms per square centimeter, i.e., inorder to remove the first or outside zone and etch into the subsurfacemetallic oxidation resistant zone. The sample was immersed in theetchant composition for a period of 20 seconds and Was bright and shinyin appearance thereafter. The sample was then heated at 350 C. in airfor a period of 2 hours. Following this treatment, the total weight gainof the sample in micrograms per square centimeter was less than themaximum sensitivity of the microbalance, i.e., the total was less thanone (1) microgram. The sample of the alloy of the present inventionremained bright and shiny after the above treatment.

EXAMPLE IV The sample was then cooled to room temperature and vigorouslyattacked wth an etchant solution as in Example II for 160 seconds inorder to remove about 13,000 micrograms per square centimeter resultingin a bright and shiny article. The sample was then heated at 350 C. inair for 2 hours and the weight gain was 21 micrograms per squarecentimeter. Following this reoxidation treatment the sample retained itsbright and shiny appearance.

EXAMPLE V An alloy was prepared in the same manner as Example I to havethe following composition: gallium 2.47 percent; silicon 3.71 percent;and the balance essentially copper.

The alloy in the mil sheet cold rolled form was carefully cleaned andheated in air at 350 C. for 2 hours. The sample showed a weight gain of22 micrograms per :square centimeter and had a slightly mottledappearance.

A fresh sample of the same alloy in the same form was cleaned and heatedat 800 C. in air for 2 hours. 'The sample was then vigorously attackedwith an etchant :solution as in Example II for 160 seconds in order toremove about 9,000 micrograms per square centimeter, i.e., in order toremove the first zone and etch into the second oxidation resistant zone.The sample was bright and shiny in appearance after this treatment. Thesample was then heated in air for 2 hours at 350 C. and showed a weightgain of 12 micrograms per square centimeter while retaining its brightand shiny appearance.

EXAMPLE VI An alloy was prepared in the same manner as Example I to havea composition of 1.03 percent aluminum; 3.88 percent germanium; and thebalance essentially copper.

The alloy in the 10 mil sheet cold rolled form was cleaned and heated at350 C. for 2 hours in air. The thus heated sample showed a weight gainof 71 micrograms per square centimeter and was darkened and mottled inappearance.

A fresh sample of the same alloy in the same form was cleaned and heatedfor 2 hours open to the atmosphere at 800 C. The sample was then cooledto room temperature and vigorously etched as in Example II in order toremove about 1700 micrograms per square centimeter and to bare thesecond zone. The etching treatment was continued for seconds and theresultant sample was bright and shiny in appearance. The sample was thenheated at 50 C- in air for 2 hours which resulted in a weight gain lessthan the maximum sensitivity of the microbalance, i.e., the total wasless than one (1) microgram, with the sample still bright and shiny inappearance.

EXAMPLE VII An alloy was prepared in the same manner as Example I tohave a composition of 1.13 percent aluminum; 4.44 percent tin; and thebalance essential copper.

The alloy in the 10 mil sheet cold rolled form was cleaned and heated at350 C. for 2 hours in air. The thus heated sample showed a weight gainof 48 micrograms per square centimeter and was darkened and mottled inappearance.

A fresh sample of the same alloy in the same form was cleaned and heatedfor 2 hours open to the atmosphere at 800 C. the sample was then cooledto room temperature and vigorously etched as in Example II in order toremove about 4200 micrograms per square centimeter and to bare thesecond zone. The etching treat ment was continued for 20 seconds and theresultant sample was bright and shiny in appearance. The sample Was thenheated at 350 C. in air for 2 hours which resulted in a weight gain of22 micrograms per square centimeter while retaining its bright and shinyappearance.

This invention may be embodied in other forms or carried out in otherways without departing from the spirit or essential characteristicsthereof. The present embodiment is therefore to be considered as in allrespects illustrative and not restrictive, the scope of the inventionbeing indicated by the appended claims, and all changes which comewithin the meaning and range of equivalency are intended to be embracedtherein.

What is claimed is:

1. A process for the preparation of a copper base alloy capable ofsubstantial resistance to oxidation which comprises:

(A) providing from 2.0 to 25 percent by weight of two elements, with theratio of the first to the second of said elements being from 0.03:1 to10:1, the first of said elements being selected from the groupconsisting of: aluminum; gallium; indium; and beryllium, the second ofsaid elements being selected from the group consisting of: silicon;germanium; tin; and beryllium, provided that when beryllium is thesecond element, aluminum is the first element;

(B) alloying-said elements with copper;

(C) heating the resultant alloy in an oxidizing environment for at leastone minute at a temperature of from 400 C. to the solidus temperature ofthe alloy to form a first outside layer 25 to 5000 Angstroms in depth ofcopper oxides and oxides of said alloy ing additions and a secondoxidation resistant layer immediately beneath said first layer, saidsecond oxidation resistant layer having a metal matrix containing adiscrete dispersion of a complex oxide including at least one of saidalloying additions, said second layer being of a thickness at least 50Angstroms; and

(D) removing said first outside layer.

2. A process according to claim 1 wherein said first and second elementsare aluminum and silicon respectively in a ratio of from 2.511 to 0.521.

3. A process according to claim 1 wherein said first and second elementsare gallium and silicon respectively in a ratio of from 10:1 to 0.211.

4. A process according to claim 1 wherein said first and second elementsare aluminum and germanium respectively in a ratio of from 5:1 to 0.2:1.

5. A process according to claim 1 wherein said first and second elementsare indium and silicon respectively in a ratio of 10:1 to 02:1.

6. A process according to claim 1 wherein said first and second elementsare beryllium and silicon respectively in a ratio of 2:1 to 0.15:1.

7. A process according to claim 1 wherein said first and second elementsare aluminum and tin respectively in a ratio of 3:1 to 0.03:1.

8. A process according to claim 1 wherein said first and second elementsare aluminum and beryllium respectively in a ratio of 10:1 to 0.511.

9. A process according to claim 1 wherein said first and second elementsare gallium and germanium respectively in a ratio of 5.0:1 to 01:1.

10. A process according to claim 1 wherein said first and secondelements are gallium and tin respectively in a ratio of 3:1 to 0.121.

11. A process according to claim 1 wherein said first and secondelements are indium and germanium respectively in a ratio of 10:1 to0.2:1.

12. A process according to claim 1 wherein said first and secondelements are indium and tin respectively in a ratio of 5:1 to 01:1.

13. A process according to claim 1 wherein said alloy is heated in anoxidizing environment for from 5 minutes to 2 days at a temperature offrom 500 to- 85 C.

14. A process according to claim 1 wherein said alloy is heated at arate of at least C. per hour to a temperature of from 600 to 800 C. andheld at that temperature in an oxidizing environment for from 1 hour tohours.

15. A copper base alloy capable of substantial resistance to oxidationcomprising:

(A) from 2.0 to 25 percent by weight of two alloying additions and thebalance essentially copper, with the ratio of the first to the second ofsaid alloying additions being from 0.03:1 to 10:1, the first of saidalloying additions being selected from the group consisting of:aluminum; gallium; indium; and beryllium, the second of said alloyingadditions being selected from the group consisting of: silicon;germanium; tin; and beryllium, provided that when beryllium is thesecond alloying addition aluminum is the first alloying addition; and

(B) said alloy having an oxidation resistant zone of at least 50Angstrorns in depth, said oxidation resistant zone having a metal matrixcontaining a discrete dispersion of a complex oxide including at leastone of said alloying additions.

16. An alloy according to claim wherein said first and second alloyingadditions are aluminum and silicon respectively in a ratio of from 2.5:1to 0.5: 1.

17. An alloy according to claim 15 wherein said first and secondalloying additions are beryllium and silicon respectively in a ratio of2:1 to 0.15:1.

18. An alloy according to claim 15 wherein said first and secondalloying additions are gallium and silicon respectively in a ratio offrom 10:1 to 0.2: l.

19. An alloy according to claim 15 wherein said first and secondalloying additions are aluminum and germanium respectively in a ratio offrom 5:1 to 02:1.

20. An alloy according to claim 15 wherein said first and secondalloying additions are indium and silicon respectively in a ratio of10:1 to 02:1.

21. An alloy according to claim 15 wherein said first and secondalloying additions are aluminum and tin respectively in a ratio of 3:1to 0.03:1.

22. An alloy according to claim 15 wherein said first and secondelements are aluminum and beryllium respectively in a ratio of 10:1 to05:1.

23. An alloy according to claim 15 wherein said first and secondelements are gallium and germanium respectively in a ratio of 5.0:1 to0.1:1.

24. An alloy according to claim 15 wherein said first and secondelements are gallium and tin respectively in a ratio of 3:1 to 0.1:1.

25. An alloy according to claim 15 wherein said first and secondelements are indium and germanium respectively in a ratio of 10:1 to02:1.

26. An alloy according to claim 15 wherein said first and secondelements are indium and tin respectively in a ratio of 5:1 to 01:1.

References Cited UNITED STATES PATENTS OTHER REFERENCES Price et al.,The Journal of The Institute of Metals, vol. 63, No. 2, 1938, relied onpages 21-28.

CHARLES N. LOVELL, Primary Examiner.

1. A PROCESS FOR THE PREPARATION OF A COPPER BASE ALLOY CAPABLE OFSUBSTANTIAL RESISTANCE TO OXIDATION WHICH COMPRISES: (A) PROVIDING FROM2.0 TO 25 PERCENT BY WEIGHT OF TWO ELEMENTS, WITH THE RATIO OF THE FIRSTTO THE SECOND OF SAID ELEMENTS BEING FROM 0.03:1 TO 10:1, THE FIRST OFSAID ELEMENTS BEING SELECTED FROM THE GROUP CONSISTING OF: ALUMINUM,GALLIUM; INDIUM; AND BERYLLIUM, THE SECOND OF SAID ELEMENTS BEINGSELECTED FROM THE GROUP CONSISTING OF: SILICON, GERMANIUM; TIN; ANDBERYLLIUM, PROVIDED THAT WHEN BERYLLIUM IS THE SECOND ELEMENT, ALUMINUMIS THE FIRST ELEMENT; (B) ALLOYING SAID ELEMENTS WITH COPPER;